Prepare and partially purify sufficient rabbit interferon with a titer of 5-10,000 units per ml. to produce 1,000 vials of an acceptable international standard reagent. Study parameters of lyophilization including pH, inert gases and stabilizers to obtain the best lyophilization process. Perform accelerated storage tests to assure stability of the material over an indefinite period. Assign a unitage to the interferon which correlates with the current wet frozen material. Lyophilize and ampoule sufficient interferon to provide the NIAID with 1,000 ampoules of a stable, potent rabbit interferon to be acceptable as an international standard.